In the Windows 8 store, I saw a link saying "Update to Windows 8.1 for free". So I clicked on it, and it downloaded, and the installation began.
But after that, it was asking me for a product key, and since I didn't have one, I skipped it, and it showed that Windows 8.1 was not activated.
Why is this? How can I fix it? The Windows 8 and 8.1 installations are both legitimate (not pirated), so I don't understand. Also, in the Windows 8.1 Store installation videos on YouTube I have watched, no such Product Key step is even shown.